When a television set owner is a subscriber to a cable television system and also possesses a videocassette recorder (VCR), he may be required to connect to the cable system via a cable decoder box (also called a CATV converter, or a set-top converter). This connection may be required, because in these systems, many cable channels (i.e., the so-called premium channels) are scrambled (i.e., encoded or encrypted) and must be descrambled (i.e., decoded or decrypted) in the cable box. The cable box descrambles the premium channel and converts its RF carrier frequency from its assigned cable channel frequency to a cable box output frequency, normally that of channel 2, 3, 4, or 5 for reception and recording by the VCR, or display by the television receiver. In such an arrangement the viewer may have as many as three remote control units for controlling the video equipment (i.e., one each for a television set, a VCR, and the cable box). If a user wants to change channels via the tuner of his cable box but inadvertently operates the remote control for the VCR, the VCR will tune away from the output channel of the cable box, causing loss of signal to the VCR, and most probably, also causing a great deal of confusion, especially to a non-technically-trained user.
A second problem arises in connection with lists of preferred channels. It is common practice to include lists of preferred channels in television receivers (TVs) and VCRs. In response to a CHANNEL UP or CHANNEL DOWN command, the TV or VCR skips non-preferred channels and tunes a preferred channel which is next higher or next lower in frequency from the currently-tuned channel. Many skip lists are automatically programmed via an autoprogram feature which steps through all possible channels and programs the skip list with information concerning whether or not each channel is active. Channels not detected in the autoprogram operation may be added by a user via operation of an ADD key. Channels which were detected and stored in the skip list but which nevertheless are not preferred by a user may be deleted from the skip list by operation of a DELETE key. Unfortunately, cable boxes normally do not perform an autoprogramming operation, and do not include skip lists. Thus, confusion arises because, a CHANNEL UP command sent to a VCR will cause the tuning of the next active or preferred channel, while a CHANNEL UP command sent to a cable box will cause the selection of the next higher channel whether that channel is active or not.